The world-wide variation in the incidence of colon cancer and the increased incidence found in migrants from low to high risk areas support the notion that environmental factors are involved in the etiology of this disease. These environmental factors are thought to be largely dietary. Furthermore, it has been hypothesized that intestinal bacteria may be generating carcinogens or co-carcinogens from bile acid substrates. The overall objective of this proposed research is to delineate the role of bile acids and the intestinal microflora in colon cancer carcinogenesis. The research goals for the coming year include 1) purification and characterization of 7-alpha-dehydroxylase from Clostridium leptum VPI 10900 and to determine if this is but one enzyme in a bile acid catabolic pathway in this organism. 2) To determine if this organism or certain other intestinal bacteria are capable of generating mutagens from media components or bile acid substrates assayed by the Ames test. BIBLIOGRAPHIC REFERENCE: Stellwag, E.J. and P.B. Hylemon. Purification and characterization of bile salt hydrolase from Bacteroides fragilis subsp. fragilis. Biochim. Biophys. Acta. 452: 165-175 (1976).